Author: Eugene Ahn

Does Sugar Feed Cancer?

The SIO Research Committee is pleased to offer this first installment in a new blog series known as “Myths of Cancer”. In this series we will address some of the most common myths and misperceptions that arise around cancer risk and treatment related to diet and natural health products, as well as other complementary therapies such as yoga, acupuncture and meditation. If you have a question you’d like us to address or comments about this post, please send your suggestions to: info@integrtiveonc.org

We hope you enjoy the series!
Linda Carlson and Eugene Ahn, Research Co-Chairs.

Co-written by Eugene Ahn, MD and Kristen Trukova, MS, RD, LDN, CNSC, CSO
© 2016 Rising Tide

Eugene Ahn, MD is the medical director of clinical research and medical oncologist at Cancer Treatment Centers of America® (CTCA) at Midwestern Regional Medical Center (Midwestern), and Kristen Trukova, MS, RD, LDN, CNSC, CSO is a clinical oncology dietitian at CTCA® at Midwestern. They are both SIO members and have a passion for education and keeping their communities up to speed on the latest in scientific research. Disclaimer: The opinions expressed here are the authors’ own, and not necessarily those of the Society of Integrative Oncology or Cancer Treatment Centers of America. The SIO and CTCA supports open dialogue between health care practitioners and patients to make sure patients can make informed decisions. As always, your comments and feedback are welcome.

There are so many questions we get from patients in our clinics that are provocative but lack simple answers, and today we tackle one of the most common questions: “Does sugar feed cancer?” To condense the topic into a blog entry, we will not address specifically a ketogenic diet (low carbohydrate and protein, high fat, caloric restriction and fasting diet), but will save that for another blog, so stay tuned!

Quick Answer Box

It’s complicated. But one should feel comfortable taking in sugars through fruits and vegetables due to their higher nutritional value and content that goes with the sugars. Some cancers might become more resistant to treatment with high sugar intake, but the science of predicting which cancers would benefit from a low sugar diet is too early in its infancy to make any general recommendations.

Let’s take a closer look at the science behind this question with the goal of determining a reasonable dietary change to impact both cancer risk and potentially cancer outcomes. One of the best principles in discerning the truth of information available on the internet is being mindful of our desire to over-simplify the complex. Answers given on the internet on this topic tend to make two erroneous assumptions 1) all cancers have the same biology and sensitivity to manipulation of sugar intake, and 2) because diet or excessive sugar consumption may increase risk of cancer, sugar cessation is an adequate treatment for cancer alone.

First, the answer to the question “does sugar feed cancer?” is yes, but it’s important to recognize that all of the cells in our bodies use glucose (blood sugar) for energy. In fact, the brain can only use glucose for energy. Even in a diet that contains absolutely no sugars or carbohydrates, our bodies have processes to convert some of the calories we consume from protein and fat into blood sugar so your brain and other tissues can function (thank goodness).

However, there is scientific evidence that high sugar intake is at least indirectly responsible for increased cancer risk. For example, research has shown that diets excessive in sugary beverages increase the risk of many cancer types (www.aicr.org). These studies point to excessive caloric intake from sugar that promotes weight gain and obesity (a known risk factor for several cancers) and secondarily increases insulin and other growth hormones in the body (which as we will learn later, is one of the proposed mechanisms by which high sugar intake could worsen cancer outcomes). What we know sugar does not do is directly damage DNA or cause cancer, but the secondary effects of excessive sugar intake – obesity and increased insulin and insulin-like growth factors – might create an environment where cancer evolution is more likely to occur.

Given that several cancers express the insulin growth factor family of receptors on its surface, it is biochemically plausible that reducing sugar intake and thereby reducing insulin and insulin growth factor levels could help improve cancer outcomes in cancers that gain survival/growth benefits through that signaling pathway. However, this has not been proven yet in rigorous, well-designed randomized clinical trials. The best evidence we have to support this concept comes from animal models. To highlight one study among several, mice implanted with prostate cancer cells that became palpable were randomized to high carbohydrate, high fat meals or low carbohydrate, high fat meals. The investigators found that the mice fed high carbohydrate meals had statistically significant higher insulin and IGF-1 (Insulin Growth Factor-1) levels and body weight as well as nearly two times greater prostate cancer cell growth (Venkateswaran V, 2007).

Evidence is less strong for human studies, but in a retrospective study, investigators found that consumption of sugary beverages correlated to shorter survival with cancers of the upper aero

-digestive tract (Miles FL, 2016). Also, individuals with Laron syndrome (mutations in the growth hormone receptor that lead to severe congenital IGF-1 deficiency, with decreased insulin/IGF-1 signaling) have reduced cancer risk.

The next question you might be asking is, why are these studies focusing on insulin levels and IGF-1 levels and not blood glucose? First, the blood glucose of these mice would likely have been normal. Our bodies have an intricate biochemical system to make sure blood glucose levels stay within a tight range (when out of balance, diabetes ensues) and insulin is a key regulator of this. But the current paradigm of understanding the harmful effects of high glucose intake is rooted in the concept of secondary hyper-insulinemia required to cope with such a lifestyle and the effects insulin, IGF-1 can have on both cancer growth and resistance to conventional treatment such as chemotherapy or hormone therapy.

For the most current understanding of how insulin, IGF1 affect cellular function, see Figure 1.

Sugar figure 1

Djiogue et al 2013 “Insulin resistance and cancer: the role of insulin and IGFs” Endocr Relat Cancer Feb 1 2013 R1-R17

The main point of showing this figure is to demonstrate the futility of making general statements like “sugar feeds cancer”, “insulin feeds cancer” or even “IGF1 feeds cancer”. The figure shows that there are several receptors that can bind insulin or IGF1. How a cancer cell reacts to insulin or IGF1 depends on the context of which, if any, of those receptors lies on its surface. For example, insulin could just simply mediate sugar metabolism (through Insulin Receptor B), or it could deliver proliferation signals through an Insulin Receptor A, IGFR-1 or a hybrid of these two receptors, and speed up cancer growth or make the cancer cells more resistant to conventional cancer treatment. Lastly, if the cell does not have Insulin Receptor A or IGFR-1 on its surface, no effects might be seen.

A closer look at the clinical relevance of the IGF signaling pathways

To avoid confusion, sugar does not specifically drive increased IGF-1 production, but the secondarily increased insulin does suppress production of insulin growth factor binding proteins, which makes IGF-1 more available to both normal and cancer cells (M, 2012). Also, drugs that have been studied in human clinical trials that target and block the IGF1R receptor have been disappointing and benefit has mainly been seen in the subset of patients who have high circulating IGF1 levels. One of the common explanations given for the disappointing results is the degree of “cross-talk” and “redundancy” between the different receptors and signaling pathways, where blocking IGF1R only inhibits one route of several by which cells are given growth stimuli. Additionally, the recent published preclinical study has demonstrated that sucrose and fructose overconsumption in mice greatly accelerates the onset and progression of breast tumors in three different mouse or human breast tumor models through modulation of inflammatory pathways, independent of weight change or blood sugar (Jiang Y, Cancer Research, 2016).

So what should I do about sugars?

Although not reviewed here, there are many long-term benefits of reducing sugar intake such as weight control. Several studies have shown women who gain weight after breast cancer diagnosis trend towards worse cancer specific outcomes and clear improvement in all-cause mortality (Playdon MC, 2015). The best anyone can say with the current science is that limiting sugar intake for someone dealing with cancer diagnosis will improve overall health and weight, and reduce side effects of cancer treatment (sugar intake can worsen hot flashes from anti-hormonal treatment). It might also enhance the benefits of conventional treatment (surgery, chemotherapy and radiation) and reduce risk of future cancer diagnoses. And for a subset of the cancers diagnosed, there might be a benefit in reducing sugar intake and secondary insulin and IGF1 availability as well as reducing inflammation on actual cancer outcomes, but the data is limited to animal studies and specific cancer cell lines.

So if one were inclined, the 2015 Dietary Guidelines for Americans encourage a limit of only 10 percent of calories per day from added sugars. For the average person, this means only 200 calories (50gm) from added sugars out of 2000 calories total should be consumed. This is a tough order. For example, a 12oz. can of soda or a single serving size of your favorite sweetened yogurt likely contains up to 40 gm of added sugars. One teaspoon of sugar is equal to four grams of sugar. Thus, sugary beverages which include soda, fruit juices, sports drinks, energy drinks and specialty sweetened coffees should be consumed only occasionally. Are these guidelines effective enough to harness a potential anti-cancer effect? We do not know. But, if your baseline sugar intake is greater than 50gm/day currently, chances are your overall health will eventually be compromised.

But thinking further, what does this mean for brown sugar, raw sugar, honey, molasses, maple syrup and jam? Beyond sweeteners, what about foods that contain natural sugars, as in fruits and plain yogurt, as well as added sugars, which include just about everything you can think of from ketchup to bread? What about carbohydrates, like starches, fruits and milks, which are broken down into sugars? What is left to eat?

Keep in mind that a plant-based diet has been found to be cancer protective. Choosing whole grains, vegetables, beans and fruits in the right portion provides important phytochemicals, antioxidants, electrolytes and fiber in addition to the carbohydrates. One key to success is to avoid “empty calories” such as soda, refined grains and highly processed foods, where very little nutritional value is being provided outside of the calories. And take the time to read the sugar content on the food labels. Find the cereals and yogurts with the least sugar possible. Eat your fruit to get more fiber/pulp in lieu of juices. And be aware that too much portions of a healthy food can still make it unhealthy from a caloric standpoint.

Finally, malnutrition and severe weight loss, especially muscle weight, is very common during cancer treatment. Adequate nutrition is critical. It has been shown that weight loss and malnutrition during cancer treatment decreases tolerability of cancer therapy and is associated with worse outcomes (Barret M, 2011). Any dietary change that results in a lower caloric intake should be reviewed by your health care provider, and other foods might be required to meet nutritional needs. Making weight loss the only end point for your dietary and lifestyle choices could lead to harmful outcomes, so please seek guidance from an available dietitian.v

The SIO Research Committee is pleased to offer this fourth installment in a new blog series known as “Myths of Cancer”. In this series we will address some of the most common myths and misperceptions that arise around cancer risk and treatment related to diet and natural health products, as well as other complementary therapies such as yoga, acupuncture and meditation. If you have a question you’d like us to address or comments about this post, please send your suggestions to: info@integrativeonc.org.

We hope you enjoy the series!
Linda Carlson and Eugene Ahn, Research Co-Chairs.

5 Common Myths About Cancer and Cancer Treatment that Could Harm You

By: Eugene Ahn, MD

Quick Answer Box

Sometimes we can hold on to our belief systems too tightly. Below, we discuss some myths about cancer that evidence suggests may negatively impact a patient’s chances of surviving a cancer diagnosis. We have intentionally excluded controversies that will be addressed in future blog entries.

A new diagnosis of localized cancer can be an emotional rollercoaster of ups and downs, dread and optimism, fear and empowerment. Added to this distress is the seemingly impossible task of gathering sufficient information to make the best evidence-informed decision regarding an optimal individualized treatment plan. It is only natural (with the lack of any editorial oversight on most information posted on the Internet), that someone could accidentally pick up some erroneous beliefs about cancer and cancer treatment and likewise miss out on important new research insights that would improve cancer treatment outcomes. In this blog, we discuss myths that already have sufficient research to show they are not only incorrect, but also may harm a patient’s chances for thriving after a cancer diagnosis. We interviewed surgical oncologists, medical oncologists and other cancer care providers to identify the most common harmful myths that they encounter in their practice. These myths are listed in order of least to most harmful.

5. After completing treatment aimed at curing cancer, the most important thing to do is to have lab and imaging tests to make sure the cancer does not come back

There are some cancers where lab tests and routine imaging are important for optimal outcomes, such as testicular cancer. But for other cancer types, we are clearly over-testing without any evidence that such practices improve outcomes. For example,in the case of breast cancer, some practitioners or patients will insist on obtaining tumor markers (blood tests for proteins that can be elevated if the cancer expresses it) despite the fact it is already established as an unreliable screening marker for breast cancer. The negative side-effects of using such tests can be huge. Imagine having an elevated cancer marker and the emotional turmoil that you would experience thinking you have a possible cancer recurrence, only to find out one year later after repeated images and tumor markers (and likely biopsies) that it is not the case. It would be more impactful to focus on primary prevention: i.e. promotion of lifestyle behaviors that would help prevent another cancer, and in some cases, reduce chances of cancer recurrence. This includes a healthier diet, more physical activity and mind-body practices, and continued secondary prevention (such as a screening mammogram, when appropriate).

4. If my doctor recommends that I see a psychiatrist or psychologist for additional consultation, they must think I’m crazy.

One of the biggest remaining stigmas about cancer care is no longer the word “cancer”, but anything that begins with the letters “psych”. In fact, that is precisely one of the reasons why supportive care clinics are not called “psychosocial care” or “psychological support”, but use terms like quality of life or survivorship clinic. But it is really an unfounded fear. People with emotional distress who receive care from a qualified mind-body support professional do significantly better in terms of both cancer-related quality of life and minimizing side effects from treatment. In fact, the ones who need mind-body support the most, often tend to be the very ones who refuse to acknowledge this as a missing essential component in their healing plan. Oncologists know that cancer treatment can be tough physically and emotionally, and their referrals to a mind-body expert are basically their way of saying there are better, more qualified specialists who can help you with the emotional rollercoaster ride that is cancer. Those that receive care from a mind-body specialist often emerge from cancer treatment with what is called “post traumatic growth” or in simpler words, a silver lining to their cancer experience. This “positive meaning” to their cancer experience has huge implications in terms of emotional well being after cancer treatment is completed.

3. It’s not cancer that kills people, it’s the cancer treatment.

While it is true that injury and even death can occur with conventional medicine and/or errors made by personnel within cancer centers, it is in the striking minority. A common narrative on alternative health websites is that when patients have metastatic cancer and receive chemotherapy, that it is the chemotherapy that ultimately kills the patient, not the cancer. This is an easy hypothesis to test. If that were true, then you would have data that consistently shows patients with cancer who die, had chemotherapy in their last month of life. In fact, when you track most cancer centers, you will find that very few patients who die from cancer, received chemotherapy in their last month of life. In a study that garnered a lot of press attention, researchers found that in England, on average 8.4% of patients with lung cancer and 2.4% of patients with breast cancer died within a month of receiving chemotherapy (Wallington et al, Lancet Oncology 2016). In fact, chemotherapy given within the last month of life is a measure by which insurance companies will measure the quality of care given at a cancer center (less treatment in the last month of life is encouraged). According to this myth, we should also be seeing scores of patients in hospice care or self-care rebounding miraculously when freed from the toxicity of chemotherapy, but unfortunately that is not reflected in the statistics. It is true that a surprising number (35%) of oncologists polled on whether they would take chemotherapy (this was before the approval of immunotherapy) if diagnosed with metastatic non-small cell lung cancer would not. However, it is erroneous to assume that this data meant those physicians believed chemotherapy would kill them. They were simply willing to acknowledge that if they were dying, they would rather focus on the time left to connect with family and get their affairs in order.

2. I can think my cancer away with positive thoughts

Probably the greatest misunderstanding regarding mind-body medicine is that you can treat cancer by simply focusing on positive thoughts or imagery. Clinical trials looking at positive visualization have been negative for overall survival with cancer, but they do help reduce anxiety and improve some measures of quality of life and may even impact immune and other biological processes. However, there is no evidence that positive thoughts result in cancer regression or cure. The idea that having negative thoughts will bring back your cancer is simply wrong and can be very psychologically harmful. In fact, one of the most powerful mind-body therapies, mindfulness meditation, emphasizes becoming a non-judgmental curious observer of ALL that is transpiring in our ‘mind’, being inclusive of both “good” or “bad” emotions and thoughts. By embracing and not fearing our negative emotions or thoughts we can then gain personal insight into what is the real cause of those phenomena, and often it is discovered that these are conditioned responses, related to past experiences but not necessarily probable outcomes in the present. The healthiest way to relate to emotions is to acknowledge, accept and experience them as they are, allowing them to come and go as they will with the recognition that all things are passing and impermanent, and not harmful.

1. I can’t do surgery on my cancer because “oxygen will feed the cancer” and make it more aggressive.

Perhaps as expected, mainly the surgeons interviewed for this blog entry reported encountering this myth, which would clearly make a patient reluctant to have their cancer surgically removed or biopsied. There are a lot of reasons why surgery might not be the best option for you (for example, it is already metastatic and spread), but when it comes to curative intent treatment of almost all solid organ cancers, surgical removal is usually the most impactful intervention to achieve cure. In fact, for pre-cancerous lesions like colonic polyps and DCIS of the breast, surgical removal alone is highly effective for prevention of evolution into malignancy and it is known that without surgery and just observation the risk of these becoming more aggressive in biology and clinical stage increases the longer you wait to remove those lesions. This belief system is more often found in African-American and Latino patients (Ann Int Med 2003), and correlates to delay or refusal of surgery. If this belief were true, however, we would expect to rarely see cases of metastatic breast cancer in patients who did not have a prior biopsy or surgery for breast cancer. Unfortunately, we know that as many as 6-10% of patients who are diagnosed with breast cancer present with metastases without a prior biopsy or breast surgery. In summary, there are much more influential factors one should be worried about (biology of the disease, genomic changes in the cancer, lifestyle choices) than being afraid of surgery.